Proceedings Paper

Infrared systems applications often require low noise detectors to achieve background limited performance. In this paper, the dark current (noise) mechanisms of InSb MIS detectors will be discussed from a theoretical viewpoint and a model of the dark current phenomena will be presented. Device measurements will be presented to qualify the model. The total well capacity of an MIS detector is determined by the insulator capacitance and the height of the applied voltage pulse that switches the device into deep depletion (Q = CoxVI. As VI is increased beyond some threshold value, the dark current is seen to increase more rapidly, leading to excess detector noise. This "breakdown" is attributed to carrier tunneling from states at the interface into the conduction band. This is due to the higher fields associated with increasing the voltage pulse height. A model that qualitatively describes this phenomenon is presented along with experimental data for InSb devices. InSb MIS infrared detectors integrate minority carriers that are generated in the potential well beneath a transparent metal gate (see Figure 1). This integrated charge is read out by collapsing the potential well, which causes the collected carriers to recombine in (or be injected into) the substrate, thereby creating a current in an external circuit. The well is then reestablished, initiating charge integration. This is the principle of the Charge Injection Device (CID).1 The collected charge includes both photogenerated carriers (which arise from incident radiation) and dark current. This paper is the result of a study of the physical mechanisms that contribute to the generation of dark carriers in CIDs which will ultimately limit the detector's performance.